1. Field of the Invention
The present invention relates to a multi-hop communication system and a multi-hop communication method, which are configured by a radio control station and radio stations. The present invention also relates to a radio control station and a radio station used in the multi-hop communication system. Specifically, the present invention relates to a cellular phone system, in which a radio base station acts as the radio control station, and a wireless LAN, in which an access point acts as the radio control station.
2. Description of the Related Art
(Ad Hoc Network)
In an ad hoc network, communications between two stations, which cannot directly communicate with each other, are achieved using multiple stations. The multiple stations relay signals transmitted by the origin to the destination (which is called “multi-hop connection”). As for the ad hoc network, various kinds of commutation route discovery protocols have been proposed, i.e., DSR (Direct Source Routing) and AODV (Ad hoc On demand Distance Vector).
In such ad hoc networks, a centralized control station like the base station in the cellular phone system does not exist. Therefore, normally the radio station itself discovers a communication route autonomously.
(Multi-hop Cellular)
In this regard, the multi-hop cellular, in which a communication route from the radio station to the base station is acquired by a multi-hop connection, has also been proposed. In the multi-hop cellar, since the radio station can access to a core network via the base station, communications with the destination becomes possible if a communication route up to the base station is acquired. Therefore, probability of connection with the distant destination is higher than the ad hoc network.
However, in the multi-hop cellular, methods of communication between the radio stations and acquisition of a communication route between the radio station and the base station have still been considered. It is highly desirable that such processes are performed within a short period of time with a small amount of controlling signals.
Further, communications cannot be performed between the radio stations if communication channels handled by the base station are fully occupied. In this case, since packets, which are not received by any radio station/base station, are transmitted, resources of the multi-hop cellular are wasted.
Moreover, it is known that in a radio communication system, higher transmission power is required as transmission speed (bit rate) increases. Therefore, power consumption at the radio station/base station may become excessive if the bit rates for transmitting both control signal and information signal are increased simultaneously.